1. Field of the Invention
The present invention relates to a piezoelectric element and its manufacturing method, and more particularly to a piezoelectric thin-film element used in an actuator or the like for precise position control of sub-micron level and its manufacturing method.
2. Prior Art
FIG. 23C is a sectional view of a general piezoelectric thin-film element 90. In this piezoelectric thin-film element 90, both principal surfaces of a piezoelectric thin-film 92 are coated with electrode metal films 94 and 96. When a voltage is applied between the electrode metal films 94 and 96, the piezoelectric thin-film 92 expands and contracts in the in-plane direction. The piezoelectric thin-film element 90 can be used as an actuator for controlling the position by making use of variation by such expanding and contracting motion.
A general manufacturing method of such a piezoelectric thin-film element 90 is explained. First, as shown in FIG. 23A, a piezoelectric thin-film 92 and an electrode metal film 94 are deposited in this sequence on an electrode metal film 96. Then, as shown in FIG. 23B, dry etching is performed by forming a mask 98 on the electrode metal film 94. As a result, the electrode metal films 94 and 96 and the piezoelectric thin-film 92 in a region not covered with the mask (indicated by arrow in FIG. 23B) are removed by etching, and a piezoelectric thin-film element 90 in a desired shape as shown in FIG. 23C is fabricated.
When the piezoelectric thin-film element 90 is fabricated by dry etching, as shown in FIG. 23C, a thin film of a side wall deposit 88 is formed on the side of the piezoelectric thin-film element 90. Components of this side wall deposit 88 include components of piezoelectric thin-film, chemical polymerization products of etching gas, and components of electrode metal film.
As the etching depth becomes greater, etching by-products are generated massively in the dry etching process, and more side wall deposits 88 are formed on the side of the piezoelectric thin-film element 90. Therefore, when the piezoelectric thin-film 92 is thick, or when the piezoelectric thin-film element 90 is composed of multiple layers of piezoelectric thin-film 92 which is thin, etching depth must be further increased, and the amount of side wall deposits 88 formed on the side of the piezoelectric thin-film element 90 increases.
Since a conductive substance is contained in the side wall deposits 88, when side wall deposits 88 are adhered on the side wall of the piezoelectric thin-film element 90, insulation between the electrode metal films 94 and 96 declines, and the electrode metal films 94 and 96 are short-circuited, and electric field is not applied to the piezoelectric thin-film 92, and thereby the piezoelectric thin-film element 90 fails to function. Accordingly, the product yield in the manufacturing process cannot be enhanced sufficiently. In addition, the multilayer lamination of piezoelectric thin-films causes the displacement of the actuator to increase, and although it is indispensable depending on the purpose of use, it was difficult to manufacture the piezoelectric element composed of multiple layers of piezoelectric elements with high reliability and high yield.